Above all, the main noise source is presumed to be from commercial ships. The sources of low-frequency noise are seismic explosion, transportation, harvesting renewable energy, and military sonar. suggested that average noise levels would increase by 2.5–3 dB per decade. indicated that low-frequency noise levels in the ocean increased by 10 dB between 1960s and 1990s. Ocean noise caused by human activities has been rapidly increasing in recent years. Dataset which was used in the localization of whales are available from the Zenodo repository ( ).įunding: This project was carried out as a research activity of underwater noise project of the Japan Ship Technology Research Association in the fiscal years 20 it had been funded by the Nippon Foundation.Ĭompeting interests: The authors have declared that no competing interests exist. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.ĭata Availability: Datasets of the song parameters of each humpback whales are within the supporting information. Received: DecemAccepted: SeptemPublished: October 24, 2018Ĭopyright: © 2018 Tsujii et al. PLoS ONE 13(10):Įditor: Songhai Li, Sanya Institute of Deep-sea Science and Engineering Chinese Academy of Sciences, CHINA Responses may differ where ship traffic is heavy, because avoiding an approaching ship may be difficult when many sound sources exist.Ĭitation: Tsujii K, Akamatsu T, Okamoto R, Mori K, Mitani Y, Umeda N (2018) Change in singing behavior of humpback whales caused by shipping noise. The focal ship was 500 m away within several minutes.
This could be a cost effective adaptation because the propagation loss at 500 m from the sound source is as high as 54 dB. In the Ogasawara water, humpback whales seemed to stop singing temporarily rather than modifying sound characteristics of their song such as through frequency shifting or source level elevation. Humpback whales reduced sound production after the ship passed, when the minimum distance to the whale from the ship trajectory was 1200 m. Fewer whales sang nearby, within 500 m, of the shipping lane. Source level of the ship (157 dB rms re 1μPa) was measured separately in deep water. In total, locations of between 26 and 27 singers were measured acoustically using time arrival difference at both stereo recorders on the ship presence and absence days, respectively.
A passenger-cargo liner was operated once per day, and other large ship noise was excluded given the remote location of the Ogasawara Islands, 1000 km south of Tokyo.
Two autonomous recorders separated by 3.0 km were used for the acoustic monitoring of each individual song sequence. Reactions of singing behavior of individual humpback whales ( Megaptera novaeangliae) to a specific shipping noise were examined.
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